The present invention relates to a method of forming a film of metallic silicide, particularly high melting point metallic silicide, and particularly to a method of controlling the composition ratio of metal and silicon.
FIG. 1 shows a thin film 3 of MoSix, an example of a high melting point metal used in fabrication of an LSI device formed by sputtering ontoi an oxide film 2 which in turn is formed on an Si wafer 1.
The composition ratio between Mo and Si of the MoSi thin film 3 formed by sputtering on the oxide film 2 is determined mainly on the composition ratio between Mo and Si of the target.
A stable composition is obtained when the ratio of Si/Mo atoms is at 2. But, the Si/Mo composition ratio of the MoSi film as a part of a semiconductor device is set to be within a range of from 2:1 to 3:1. This is because the excessive Si in the MoSi film will cause a favorable stress, and thereby prevent peeling-off of the MoSi film, which may otherwise occur during heat treatment for recrystallization of the MoSi deposited by sputtering on an Si wafer. But as the ratio of Si/Mo atoms is set to b 2.0 through 3.0, the film resistivity is much higher than the silicide film with stoichiometry, i.e., of the ratio of 2.0. The resistivity of the conductor is therefore higher, and the operation speed of the LSI is lowered.